1. Field of the Invention
The invention relates to a lighting module notably for motor vehicles, the lighting module comprising a first lighting function of the low-beam type with an essentially horizontal directivity of the beam. More particularly, the invention relates to a lighting module comprising a second lighting function of the high-beam type provided by an additional beam completing the high-beam beam.
2. Description of the Related Art
A lighting module comprising two reflectors of the ellipsoidal type is known from the Patent document U.S. Pat. No. 4,914,747. These two reflectors correspond to semi-ellipsoids and are superposed with their reflecting surfaces oriented towards one another, i.e. in an opposing fashion. The module comprises a specific light source for the upper reflector and a common light source for the two reflectors, the specific light source being situated at the focal point of the upper reflector in order to participate in the formation of an illuminating beam of the low-beam type and the common light source being situated at the focal point of the lower reflector in order to participate in the formation of an illuminating beam of the high-beam type. A horizontal shield with a cut-off edge is provided close to the second focal points of the two reflectors. A lens is disposed after the shield with its optical axis coinciding with the optical axis of the module. The lens is disposed in such a manner that its first focal point is close to the second focal point of the reflectors. In order to form the low beam, the light rays emitted by the specific light source of the upper reflector are reflected by the internal surface of the reflector approximately towards the second focal point of the reflector. A part of the rays pass in front of the cut-off edge of the shield. These rays encounter the lens within its lower half and are then refracted upwards. The shield blocks a part of the rays which otherwise would encounter the lens within its lower half and would form the upper part of the beam emitted after passage through the lens. The low beam thus has an upper limit referred to as cut-off. In order to form the high beam, the light rays emitted by the common light source are reflected by the upper reflector towards the lower part of the upper half of the lens and also by the lower reflector towards the second focal point of the reflector. In a similar manner to the rays emitted by the specific light source of the upper reflector, a part of the rays pass in front of the shield and encounter the upper half of the lens. Another part of the rays is reflected by the shield or reflected by a reflecting part of the latter, so as to then be refracted by the lower part of the lens in order to form the upper part of the beam, which has a lower cut-off. The position of the shield therefore determines the cut-off of the upper part of the beam, which is added to the lower part of the beam coming from the lower reflector. This superposition allows a beam to be obtained that will provide the high-beam function. This module exhibits a region of less intense illumination at the cut-off in the beam of the high-beam type and corresponds to a particular embodiment of U.S. Pat. No. 4,914,747. Furthermore, the lower part of the beam is a particular case because it originates from an unfocussed source.
What is needed, therefore, is a module that provides an improved lighting function.